Sound-reproducing device



June 24, 1930. H. c. MUELLER v 1,767,546

SOUND REPRODUGING DEVICE Filed Oct. 21, 1926 2 Sheets-Sheet l 55Tufenjfo-r June 24, 1930. H. c. MUELLER 1,767,546

SOUND REPRODUCING DEVICE qes' l i?" l W fw' Patented .lune 24, 1930UNITED s'irzx'riazsA HERMAN C. MUELLER, iOF MILWAUKEE, WISCONSINSOUND-REPRODUCING DEVICE Application led ctober'21, 1926. Serial No.143,103.

My invention relates .to a loud speaker unit more especially intendedfor use in connection with radio reception; the invention having for itsobject the provision of a device properly sensitive to the pulsations oractuating current changes and adapted to reproduce the tonalcharacteristics of the modulating medium, whether voice or instrument,employed at the broadcasting station.

Another object of my invention is the provision of a constructionwherein the dia-4 phragm is so constructed and mounted that it will bemaintained under tension and eliminate as far as possible anySympathetic and synchronized vibrations that may be set up and whichwill provide proper and natural tonal effect, While at the same timepreventing possibility of the diaphragm becoming locked to either one ofthe pole pieces of the reproducer.

The above enumerated objects as Well as other objects and advantagesinherent inthe construction will be readily comprehended from thedetailed description of the accompanying drawings, wherein- Figurel isan elevationof aloud speaker o' horn illustrating in dotted lines anapplication of my improved unit.

Figure 2 isr a vertical sectional View of the unit and. lower or baseportion of a horn.

Figure 3 is a cross sectional view taken on the line 3-3 o Figure 2lookingin ythe D direction of the arrows.

Figure 4 is an end elevation'of my improved unit with a portion of thehousing or casing shown in' section. i

40 Figure 5 is an enlarged sectional view taken substantially on theline 5-5 of Figure 4 looking in the direction of the arrows.

Figure 6 is a sectional view taken substantially 'on the line 6 6 ofFigure 5 look ing in the direction of the arrows.

Figure 7 is a detail perspective view of a pole piece separating memberand armature support holding member.

Figure 8 is a detail perspective view of my improved armature.

In the particular exemplificationof the invention as disclosed in thedrawings, my

improved loud speaker unit is shown apv plied to the well known type ofhorn 15, see Figure l1, with the unit indicated in dotted lines at 16mounted in the base portion and in communication with the small .of hornor other sound amplifying device.

For purposes of illustration, my improved unit is mounted in the base, aportion of which is shownlat "L in Figure 2, by having the externallythreaded hub 17 of the cover plate 18 screwed into the throat of thebase portion of the horn in alignment with the inlet or small end of thehorn. The cover plate or member 18, and the shell member 19, arepreferably annular and of suitable thickness to provide rigidity. Thesetwo members 18 and 19 are secured together by suitable'means, as forexample the screws 20. The cover ymember 18 is provided with a beveledcircumferential groove 21 withl the bevel formed so that the grooveincreases in depth toward the periphery of the cover member 18. Thecover member is centrally provided with the outlet opening 22 which ispreferably provided with thevus'ualscreen indicated at- 23 toprevent Yingress of foreign matter.

The shell or annular member 19 is dished or cupped to provide a suitablechamberv between it and the cover member 18 wherein the diaphragm 24 islocated; that is to say, the shell'19 is provided at ,its outerperimeter with an annular shoulder 25 which comes into abutting relationwith the cover member 18;'the main body portion of `the shell 19 beingprovided with a suitable number of openings 26 and with'the largecentral opening 27 through which the stylusbar 28 passes. The shell ormember 19, adjacent to the annular shoulder 25, is also provided with anannular beveled groove 29, which, like the groove 21, in cover member18, increases in depth ltoward the outer perimeter or annular shoulder25. The shell 19, at the inner perimeter of the groove 29, is preferablyformed with an annular ridge as at 30, see Figure 5. The annular grooves21 and 29 are intended to receive the flat gaskets 31, 31, preferably ofrubber, which are mounted adjacent to the perimeter of the diaphragm 24,both on the up er and lower sides thereof. As a result of t isconstruction, when the shell 19 and covermember 18 are secured together,the flat gaskets will be forced toward the deeper portions of thegrooves that is to say will be squeezed outwardly and uniformly aboutthe entire perimeter of the diaphragm which has the effect or tendencyto stretch the diaphragm outwardly and consequently holds the diaphragmtightly. Mounting the diaphragm in the manner shown and described, willvhold it under'constant tension and the pitch of the diaphragm thusmaintained. This method of mounting at the same time preventspossibility of the diaphra, ;m becoming locked to either one of the polepieces. l I also prefer to have the diaphragm 24 circumferentiallycorrugated, as shown, thereby permitting the. use of a lighter diaphragmand one made of softer material than otherwise would be the case. Thecenter of the diaphragm is preferably dished or concaved as shown at 32where it is secured to the stylus bar 28.

A permanent magnet 33 is disposed beneath the shell 19 with the ends ofthe magnet provided with extensions o-r pole pieces 34, 34, of U-shapein cross-section, having upstanding ends or lips 35 adapted to en gagewith the sides of the permanent mag'- net 33. The sides of the polepieces, secured to the two ends of the permanent magnet, are disposedtoward each other and terminate in slight spaced relation as shown inFigures 2, 4, 5 and 6. The sides of the pole pieces are adapted toextend" along opposite sides of a suitable electro-magnet or coil 36which is preferably formed into the oblong configura-tion shown inFigures 4 and 6. The electro-magnet or coil 36 is provided with asuitable insulating tube or core 37 formed to receive a member 38 shownin Figure 7. The member 38 is provided with the bent sides 39, 39 whichpreferably extend slightly beyond the ends of the member as shown at 40in Figure 7; and the member is transversely slotted as shown at 41..kThe extended ends 40 provide shoulders for the sides of the pole pieces34 and maintain their proper spaced relation; the pole pieces thereforemaintain the plate 38 in position within the core of the electro-magnetor coil 3G. This member constitutes a po-le piece separating member andarmature support holding member.

With the member 38 formed as shown it is apparent that a small space orchalnber between the member and one side of the insulating tube or core37 is provided to receive the vibration element or armature 42 which isshown in detail in Figure 8.

The armature comprises a plate, preferably .of the rectangularconfiguration shown and provided longitudinally with a depression orrigidifying surface 43- which acts as a stiifener and eliminatesvibration being set up in the armature itself. One side of the armature42 is provided with a bridge or feather 44 eX- tending transversely ofthe armature. This feather 44 is made of comparatively thin sheet metalor other suitable material having depending ends 45, 45 which extendinto slits in opposite sides of the armature `as shown at 4:3 in Figure8, with one of the depending ends on the lower side of the armature bentlaterally in one direction, while the other depending end is bentlaterally in the opposite direc-tion. This holds the bridge or featherin place without too rigidly holding the armature. The armature isplaced beneath member 38 between the downwardly bent sides 39, 39, withthe bridge or feather 44 inserted in the slit 41 from the lower side asviewed in Figure 7. As the body portion of the member 38 extends iushwith one side of the insulat? ing tube. or core 37, see Figure 5, it isapparent that too far upward movement of the feather or bridge 44through the slit 41 is impossible, with the result that the armature 42is heldin spaced relation with the member 38 and the opposite side ofthe insulating tube or core 37 and is thus free to oscillate or vibrateby reason of the minute play of the feather or bridge in the slit, theplay between the feather and the armature due to the bending of the endsof the feather in opposite directions as previously described, as wellas the flexibility of the bridge or feather. One end of the armature 42is preferably provided with a projecting lip or portion 46 which isapertured at 46 to receive the end of the stylusbar 28 which may besoldered or otherwise immovably secured thereto.

The permanent magnet with the pole pieces and the electro-magnet or coil(mounted within the permanent magnet at the ends thereof), together withthe armature and its mounting, are held in place against the shell 19 bymeans of a clamping bar 47 disposed transversely of one leg of thepermanent magnet. The bar 47 is secured to the shell 19 by the screws48, 48. The clamping bar 47 is provided with suitable binding posts 49,49 to receive the wires or terminalsI 5t). :30 which go to the outputend of the receiving set.: the binding posts 49, 49 being` properl \rinsulated from the clamping bar 47 by suitable insulating washers 5l andthese posts on what may be. termed the lower ends receive the leadsv5;). 52 from the electro-lmlgnetor coil 3G.

lill.'

The stylus-bar 28, preferably .adjacent to its point of attachment tothe, armature,

is provided with a flattened portion, as at 53, see Figures 2 and 5, soas to provide a flexible point; the flattened portion being parallelwith the armature.

I have shown what is believed to be the simplest embodiment of myinvention and have described the same in terms employed merely as termsof description and not as terms of limitation, as structural modifications may be made without, however, departing from the spirit of myinvention'.

What I claim is 1. A device of the character described comprising ashell provided with Ia diaphragm, a permanent magnet mounted on theshell and provided with an opening through one end thereof, aligned polepieces disposed wholly within the ends of the magnet and secured theretoin opposing and slight spaced relation with each other, a coil disposedtransversely within the opposing pole pieces and provided with anonmagnetic core arranged in alignment with the spacing between the polepieces, a transversely slotted plate within the core of the magnet coilprovided with extended -ends disposed intermediate of opposing ends ofthe pole pieces to maintain the latter in spaced relation and to besupported in place by ksaid pole pieces, an armature provided with atransverse bridge mounted in the transverse slot of said plate fortiltably mounting the armature, one end of the armature being providedwith an extension disposed beyond the inner sides ofthe pole pieces, anda stylus-bar secured to said extension and disposed through the openingin the leg of the permanent magnet and secured to said diaphragm.

2. In a device of the charatcer described, a permanent magnet, olepieces mounted wholly within the endg of the permanent magnet and inopposing relation with each other, the ends of the pole pieces havingflanges for clamping the sides of the permanent magnet, a coilmounted'within the pole pieces and disposed transversely of thepermanent magnet, said coil being provided with a non-magnetic core, asupporting member arranged Within the core of the coil and provided witha transverse slot, an armature provided with an upstanding feather i'adapted to enter the slot in said plate, one

end of the armature being provided with an f extension, and a stylus-barsecured to said extension.

3. A device of the' character described, comprising a shell, a coverplate for said shell provided with an opening, the shell and cover platebeing provided on their opposing faces with outwardly beveled grooves, adiaphragm mounted between the shell and cover plate, yielding means disposed on opposite sides of the diaphragm adjacent to the perimeterthereof and seatable in said grooves whereby the diaphragm is maintainedunderconstant tension, a permanent magnet mounted on the shell, polepieces secured to the ends ofthe magnet in opposing relation with eachother, a coil disposed within the pole pieces, an armature tiltablymounted in the coil, and a stylustar secured at one end to said armatureand at the other end yto said diaphragm.

4. In a device of the character described, an. armature of thin sheetmaterial provided with a rigidifying surface disposed lengthwisethereof, the o posite sides'of the ari mature being slotte ,a yieldableelement ar.- ranged transversely of the armatureiwith the ends thereofdisposed through the slots in the armature and bent in lateraldirections to permit tilting of the armature.

5. In a device of the character described, a permanent magnet, polepieces secured to the ends of the magnet and disposed wholly within thelatter, a coil mounted within the pole pieces transversely thereofv andhaving a non-magnetic core, a non-magnetic plate having angularlydisposed sides mounted within the core of the coil and 'having extendedshoulders disposed between the opposing ends lof the pole pieces, saidplate. being provided with a transversey slot, an armature of thin sheetymaterialformed to prevent vibration in the'body of the armature andhaving slots atopposite sides, a feather dis osed transversely ofy thearmature and a apted toenter the slots in said plate, the body of thefeather being in spaced relation with the armature while the endsthereof are disposed through theslots in the armature andbentV inlateral directions on the opposite face ofthe armature.

6. In a device of the characterdescribed, a shell, acover plate for saidshell, the shell and cover plate being'formed to provide a diaphragmreceiving chamber. therebetween, a diaphragm of thin sheet materialcircumferentially corrugated intermediate `of the axis and the perimeterthereof, and means intermediate of the shell, the -cover plate and theperimeter of thefdiaphragm whereby the latter is placedunder astretching tension.

7. In a device of the character described,

ed on opposite faces of the diaphragm at the perimeter thereof andseatable in the grooves of the shell and the.- cover plate whereby thediaphragm is maintained u'nder tension. y

8. A device of the character described, comprising a shell provided witha central opening and with a peripheral shoulder, a cover plate for saidshell secured to said shoulder and having a central outlet opening, acircumferentially corrugated ,diaphragm of thin sheet tensible materialhaving a dished center, means disposed between the shell, the coverplate and the perimeter of the diaphragm whereby the latter ismaintained under constant tensile action, a permanent magnet mounted onthe lower` side of the shell and provided with an opening through oneend thereof adapted to register with the opening in the shell and theaxis of the diaphragm, pole pieces secured t0 the ends of the permanentmagnet and disposed wholly therewithin, a coil mounted ltransverselywithin the pole pieces with the core in alignment with the spacingintermediate of the opposing ends of the pole pieces, an armaturetiltably mounted at its center within the core of the coil, one end ofthe armature having an extension disposed beyond the inner sides of thepole pieces, and a stylus-bar secured to said armature extension anddisposed through the opening in the permanent magnet and the shell andsecured to the dished center of the diaphragm.

9. In a sound reproducing device, a magnet provided with opposing polepieces arranged on the inner opposing faces of said magnet and ofchannel formation, said pole pieces being disposed wholly within themagnet and extending in the direction of the line of magnetic flux andarranged to provide a space between the opposing ends of said polepieces, the base of the pole pieces at opposite sides being outwardlyfianged to engage opposite faces of the magnet ends, a coil mounted inthe pole pieces with its core aligned with the space between theopposing pole piece ends, and a rigidified armature tiltably mountedwithin said coil and having an extension between the opposing ends ofsaid pole pieces.

l0. In a sound reproducing device, a magnet, pole pieces disposed whollywithin the magnet in `aligned relation with each other so as to extendin the direction of the line of magnetic flux and to provide a spacebetween the opposing ends of the pole pieces, a coil mounted in the polepieces with its core aligned with the space between the pole pieces, aflanged spacing plate located in the coil core with the ends of theplate flanges arranged between the opposing pole pieces to maintaintheir spaced relation, an armature arranged in the core of said coiladjacent to said plate with its end disposed into said space and flexingmeans disposed transversely o the armature intermediate of its ends andmounted on said spacing plate so as to permit tilting movement of thearmature.

11. In a sound reproducing device, a coil provided with a core, atransversely slotted plate in the lcore of the coil, an armature of thinsheet material provided with an upstanding flexing portion arrangedtransversely of the armature and adapted to seat in the slot of saidplate to constitute a fulcrum for the armature, the armature beingprovided with a rigidifying surface disposed in a direction transverselyof said upstanding portion. i

12. In a device of the character described, a permanent magnet, polepieces composed of sheet metal bent into U-shape with opposite ends ofthe base portions bent outwardly to engage with opposite sides of therespective pole ends of the magnet, said pole pieces being locatedwholly within the magnet adjacent to the ends with the pole piecesaligned with each other, a coil arranged within the pole pieces with itscore aligned with the spacing between the ends of the pole pieces, aspacing plate located within 'the core and having extensions on its endsarranged between the opposing ends of the pole pieces whereby the latterare main- 'tained in spaced relation and said plate held in place, andan armature tiltably mounted on said plate.

HERMAN C. MUELLER.

loo

